ChemPhotoChem最新文献

Chiral liquid crystals (LCs) are essential for optoelectronic devices. Two representative achiral luminescent compounds, pyrene and perylene, are doped into a mixed chiral nematic LC (N*-LC) comprising achiral LC 4′-pentyl-4-biphenylcarbonitrile (5CB) and chiral LC 2-octyl-4-[4-(hexyloxy)benzoyloxy]benzoate (2OHBB). Consequently, despite being achiral luminescent materials, the doped pyrene and perylene successfully generate strong circularly polarized luminescence (CPL) from the resulting chiral N*-LC composed of 5CB and 2OHBB. The rotation direction of the extracted CPL can be controlled by the chirality of the LC molecule 2OHBB. Furthermore, these N*-LCs demonstrate continuous and reversible CPL responses depending on the presence or absence of a direct current (DC) electric field. This result demonstrates the successful design of a CPL LC system, where the rotation direction of CPL can be controlled not only by the chirality of 2OHBB, but also through the ON–OFF–ON switching of the DC electric field. This behavior is attributed to a reversible transition from a helical structure to another ordered structure (chiral nematic phase to chiral nematic phase transition). This study provides an effective strategy for controlling CPL properties by exposing N*-LC to DC electric fields and for developing functional CPL devices.

A Ruddlesden–Popper phase-layered perovskite Fe₂SnO₄ is coupled with graphitic carbon nitride (gCN) in an S-scheme heterojunction. The Fe₂SnO₄/gCN heterojunction is synthesized using the sonication–calcination method. The layered structure of Fe₂SnO₄ enhances charge migration toward the junction interface and enables the internal electric field, increasing the charge separation in the overall composite. The optical characteristics of Fe₂SnO₄/gCN show an excellent visible light utilization ability, thus expanding its applicability in solar (visible light)-driven catalytic approaches. A significant formate generation rate (2.043 mM h⁻¹ gcat⁻¹) is measured over the photocatalyst using the aqueous bicarbonate as the CO₂ precursor. The isotope labeling test corroborates the generation of formate from bicarbonate. Fe₂SnO₄/gCN also displays a good stability over five reaction–regeneration cycles. The band structure of Fe₂SnO₄/gCN in conjunction with the radicals detected via spin trapping confirms the development of the S-scheme heterojunction in Fe₂SnO₄/gCN. Herein, the fabrication of the layered perovskite-based S-scheme heterojunction paves a path for pursuing the solar-driven environmental remediation strategies.

Herein, a series of supramolecular electro-optic (EO) dendrimers (EOD1-6) constructed using push–pull tetraene chromophores (PPT-phores) and Fréchet-type generation-1 benzyl ether dendrons with 2,3,5,6-tetrafluorophenyl or 2,4,6-trifluorophenyl groups at the periphery is presented. The fluorophenyl moieties possess enhanced CH acidity to form extended CH···F hydrogen bonds within complex functional dendrimers. Through comprehensive studies of optical absorption, electric field poling, EO activity, and thermal stability of EOD1-6/poly (methyl methacrylate) films, along with X-ray analyses of dendritic model compounds, it is elucidated that nonclassical hydrogen bonding of fluorophenyl synthons plays a pivotal role in modulating the strong dipole–dipole electrostatic interactions of PPT-phores. It facilitates the dipole orientation and enhances the stability of supramolecular EO dendrimers in poled films. Two of these dendrimers exhibit large r₃₃ values of ≈170 pm V⁻¹ at 1306 nm and ≈120 pm V⁻¹ at 1541 nm, among the best EO activities to date for organic materials as certified by prism-coupled attenuated total reflection spectroscopy. Furthermore, examining subgap absorption for the films provides insights into the Urbach energy tail states. The notable properties and synthetic efficacy demonstrated by these dendrimers represent a transformative step in developing highly efficient, thermally stable, and low loss supramolecular organic EO materials for photonic applications.

Easily accessible small organic fluorophores with multiplexing capabilities are of interest for a variety of fields. Here, a combination of experimental and computational methods reveals previously unknown, yet potentially useful properties of one of the original squaraine dyes, i.e., bis-kryptopyrrol-2-yl squaraine. The rotational flexibility of the pyrrole units around the squaraine core allows for this dye to act as a viscosity probe. In addition to the previously known fluorescence emission in solution with λ_em in the 550–580 nm range, this dye exhibits solid-state emission with λ_em at ≈800 nm. Thus, this dye is a dual-state emitter. density functional theory/time-dependent density functional theory calculations and concentration-dependent studies, in both solution and solid-state, indicate aggregated form of these dyes is responsible for the solid-state emission in the near-IR range.

While pursuing the exploration of porphyrin/fluorene combinations at the molecular level and their application as luminescent photosensitizers for two-photon photodynamic therapy (2P-PDT), we wondered about the impact of adding electron-releasing endgroups to these molecular structures. Furthermore, we also wondered about the influence of spacers within the arms of these star-shaped architectures and about the impact of the metalation of these free-base porphyrins by zinc. To address these questions, we synthesized a series of ten novel star-shaped meso-tetraarylporphyrins, featuring various aromatic rings with 1,2-ethenyl fluorenyl and/or 1,2-ethynyl spacers, capped by diphenylamine endgroups. The linear and nonlinear optical properties of these compounds were characterized through absorption, emission, and two-photon excited fluorescence studies, thereby screening the impact of endgroups, metalation and arm composition on the optical parameters of interest. Subsequently, their singlet oxygen-photosensitizing properties were also evaluated. The enhanced properties observed for compounds presenting diphenylamino (DPA) endgroups in comparison to analogs with none, along with the impact of metalation by Zn(II) and that of 1,2-ethenyl versus 1,2-ethynyl linkers on these, were eventually analyzed using classical figures of merit. This contribution highlights the strong potential of DPA-capped star-shaped free-base porphyrins as fluorescent photosensitizers for combined 2P-PDT and imaging applications.

Understanding the mechanism through which a photochemical reaction proceeds grants access to thermodynamic and kinetic parameters that allow its optimization for large-scale applications. In the last few years, photocatalytic systems have been major players in scientific developments on research fields of primary importance, including solar fuel generation in artificial photosynthesis, and the use of excited organic radical ions as photocatalysts in thermodynamically challenging reactions of utmost synthetic relevance. Generally, time-resolved spectroscopic approaches are the main experimental tools to investigative the dynamics of photoactive systems, with pump-probe-based ones being the golden standard in photophysical and photochemical research. However, for photocatalytic systems in which multiple photons are required, which is generally the case for photosynthetic reactions and those promoted by excited organic radical ions, the pump-probe approach is no longer sufficient since it is based on a single photon-to-electron ratio. This is where a second actinic pump excitation comes into play in what is known as pump-pump-probe spectroscopy. In this review, we explore how this approach is used to unravel the mechanism of photocatalytic systems triggered by light using different probes of UV–vis absorption and resonance Raman scattering in varying time scales.

A visible light photoswitchable diarylethene–perylenebisimide (DAE–PBI) dyad, incorporating bromine heavy atoms and a ketone linker in the molecular framework, is developed. In order to enhance the visible light-induced cyclization reactivity of a DAE–PBI dyad, in this study, an “internal heavy atom effect” with the “El-Sayed rule” into the molecular design is incorporated. From the theoretical calculation on the contribution ratio of bromine atoms to the molecular orbital (MO) in lowest unoccupied molecular orbitals (LUMOs) and the value of spin–orbit coupling, it is expected that the designed DAE–PBI dyad has high reactivity for visible light-induced cyclization reactions. The synthesized dyad exhibits efficient visible light-induced cyclization reaction not only in heavy atom-containing solvents but also in typical heavy atom-free solvents. These results indicate that the combination of the internal heavy atom effect and the El-Sayed rule effectively contributes to the visible light-induced cyclization reactivity in the dyad. These results will pave the way for new molecular designs to develop UV-free photoswitchable molecules.

Rare-metal-free luminophores that exhibit room-temperature phosphorescence (RTP) in the solid state and polymer film have attracted significant attention in various fields, including imaging, sensing, and optoelectronic technologies. Herein 1,4-dibenzolyl-2-siloxy-5-(silylmethoxy)benzenes are reported as novel RTP luminophores. Thermal analysis reveals that the unsymmetrical molecular structure of the benzene derivatives results in lower melting points compared to their symmetrical counterparts. Their solid-state RTP is highly dependent on the siloxy group. The choice of tert-BuPh₂SiO group is essential for achieving efficient RTP in the microcrystalline state; the quantum yields ranged from 0.40 to 0.58, unlike the choice of tert-BuMe₂SiO. Notably, poly(methyl methacrylate) films doped with the benzene derivatives emitted RTP under vacuum conditions with quantum yields ranging from 0.06 to 0.09, irrespective of the siloxy group. Theoretical calculations suggest that the RTP occurs via excitation involving intramolecular charge-transfer from the siloxy and silylmethoxy moieties to the benzoyl groups, followed by intersystem crossing from the lowest singlet excited state (S₁) to the second-lowest triplet excited state (T₂), and subsequent internal conversion to the lowest excited triplet state (T₁). Furthermore, the polymer film doped with one of the benzene derivatives is demonstrated to function as a molecular oxygen scavenger within a polymer matrix.

In this study, it develops a series of slight Förster resonance energy transfer (FRET) systems incorporating donors (DP5 or the mixture of DP5 and PZ-Br) and acceptors (PZ-Br or Rh-COOH) through host–guest interactions. Within these FRET systems, the energy transfer efficiency reaches up to 58%. Notably, by precisely tuning the self-assemblies between the donors (DP5 or the mixture of DP5 and PZ-Br) and acceptors (PZ-Br or Rh-COOH), this study achieves tunable multicolor emissions without the need for complex synthesis or structural modifications. Most importantly, irradiating the FRET system containing the mixture of DP5 and PZ-Br and excess Rh-COOH with a 365 nm lamp for 45 min results in a system capable of tuning fluorescence from pink to pure white or even yellow. Furthermore, these FRET systems can be employed in the fabrication of white-light fluorescent films. These recent findings highlight an additional and promising application of Pillar[n]arenes in the development of white-light emission materials.

A protocol for the synthesis of sterically hindered 9-silylacridines via lithiation/silylation sequence is developed. The photocatalytic efficiency of obtained acridines is tested in a variety of decarboxylative processes and compared with the properties of aryl- and alkyl-substituted analogs. To explain the observations, quantum chemical calculations are carried out, revealing the features of the spatial structures of these molecules.